1. Field of the Invention
The present invention relates to novel compounds having the formula (I): ##STR2## wherein A is --CH.sub.2 --, --O--, or --S--; R.sup.1 is CH.sub.3 or OCH.sub.3 ; R.sup.2 is hydroxy or carboxy which may be optionally esterized or amidated; R.sup.3 is H or a lower alkyl; and n is 0 or an integer of 1 to 6, and an improver for cerebral insufficiency caused by cerebral ischemia containing the same.
The above-mentioned compounds (I) are effective for ameliorating and curing (or treating) various symptoms based on cerebral organic disorders as an oral medicine.
The term cerebral organic disorders, used herein means various symptoms derived from cerebral ischemic diseases such as cerebral infarct sequela, cerebral hemorrhage sequela, and cerebral arteriosclerosis sequela and various organic disorders derived from senile dementia, dementia presenilis, amnesia, cephalic traumatic sequela, and cerebral operation sequela.
2. Description of the Related Art
The average human life-time has become prolonged, and the percentage of old people in the population is increasing. Accompanying this increase, senile dementia such as memorial dementia characterized by a loss of the memory function as a primary symptom is becoming a serious social problem.
At present, a large number of therapeutic drugs for senile dementia have been developed, but a satisfactory drug has not been developed yet.
The brain is an organ in which energy metabolism is most active, and if a disorder in the oxygen supply mechanism within the brain occurs, and an oxygen deficiency state (cerebral hypoxia) continues in the brain cells, a state will be finally reached in which no oxygen is supplied (cerebral anoxia). If such a state continues, the brain cells will be irreversibly damaged and will no longer be able to perform their normal functions.
At present, in the therapy of oxygen deficiency diseases accompanied by cerebral hypoxia or anoxia, a hypnolic such as phenobarbital has been employed, but the use thereof is limited because of the accompanying side effects on respiratory organs or the circulatory system.